This relates to touch screen systems and methods having integrated transparent conductive material resistors. The transparent conductive material resistors can be make from indium tin oxide (ITO), conductive clear polymer, antimony tin oxide (ATO), or other suitable materials.
There exist many styles of input devices for performing operations in a computer system. The operations generally correspond to moving a cursor and/or making selections on a display screen. By way of example, the input devices may include buttons or keys, mice, trackballs, touch pads, joy sticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as to their declining price. Touch screens allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen recognizes the touch and position of the touch on the display screen and the computer system interprets the touch and thereafter performs an action based on the touch event.
Touch screens typically include a touch panel, a controller and a software driver. The touch panel is a clear panel with a touch sensitive surface. The touch panel is positioned in front of a display screen so that the touch sensitive surface covers the viewable area of the display screen. The touch panel registers touch events (the touching of fingers or other objects upon a touch sensitive surface) and sends these signals to the controller. The controller processes these signals and sends the data to the computer system. The software driver translates the touch events into computer events.
Touch panels can include an array of touch sensors capable of detecting touch events. Some touch panels can detect multiple touches (the touching of fingers or other objects upon a touch-sensitive surface at distinct locations at about the same time) and near touches (fingers or other objects within the near-field detection capabilities of their touch sensors), and identify and track their locations. Those touch panels capable of detecting multiple touches may be referred to as multi-touch panels.
Mutual capacitive touch panels can be formed from rows and columns of traces on opposite sides of a dielectric. At the “intersections” of the traces, where the traces pass above and below each other (but do not make direct electrical contact with each other), the traces essentially form two electrodes with a mutual capacitance therebetween. To scan a sensor panel, a stimulus can be applied to one row with all other rows held at DC voltage levels. When a row is stimulated, a modulated output signal can be capacitively coupled onto the columns of the sensor panel. The columns can be connected to analog channels (also referred to herein as event detection and demodulation circuits). When the panel is touched or nearly-touched, a small amount of charge is drawn to the point of contact. For every row that is stimulated, each analog channel connected to a column generates an output value representative of an amount of change in the modulated output signal due to a touch or hover event occurring at the sensor located at the intersection of the stimulated row and the connected column. After analog channel output values are obtained for every column in the sensor panel, a new row is stimulated (with all other rows once again held at DC voltage levels), and additional analog channel output values are obtained. When all rows have been stimulated and analog channel output values have been obtained, the sensor panel is said to have been “scanned,” and a complete “image” of touch or hover can be obtained over the entire sensor panel. This image of touch or hover can include an analog channel output value for every pixel (row and column) in the panel, each output value representative of the amount of touch or hover that was detected at that particular location.
Metal traces that are etched into the touch panels can be used to transmit charges from the panel surface to the event detection and demodulation circuits connected to the panel. As the size of a touch screen increases, the length of the metal traces etched into the touch panel also increases. These longer metal traces can act as antennas and cause radio-frequency interference (RFI) signals to be brought into the touch panel circuits and controller. RFI is any undesirable RF signal that interferes with the integrity of electronics and electrical systems. These RFI signals may adversely affect the operation of the touch screen.
Accordingly, what is needed are systems and methods for reducing the affect of RFI signals in touch screens.